It is my understanding that the 2011+ Allison controls the line pressure through the TCM, unlike all previous Allisons. Given that, a trans tune would be highly recommended any time you get an ECU tune to increase line pressure to match the increased torque, which will help keep the trans in one piece. Getting to adjust your shift points is just a bonus.
On the older trucks, I wouldn't do a trans tune unless you wanted/needed different shift points.